media: ov5640: Init properly the SCLK dividers

The SCLK and SCLK2X dividers are fixed in stone in the initialization
array. Let's make explicit what we're doing and move that away from the
huge array to the initialization code.

Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>